<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body id="app">
  <!-- 添加React的依赖 -->
  <script src="https://unpkg.com/react@16/umd/react.development.js" crossorigin></script>
  <script src="https://unpkg.com/react-dom@16/umd/react-dom.development.js" crossorigin></script>
  <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
  <script type="text/babel">
    class App extends React.Component {
      constructor() {
        super() // 初始化
        this.state = {
          message: "Hello World"
        }
      }
      render() {
        return (
          <div>
            <h2>{this.state.message}</h2>
            <button onClick={() => { this.btnClick() }}>按钮</button>
          </div>
        )
      }
      btnClick() {
        this.setState({
          message: 'Hello React'
        })
      }
    }
    ReactDOM.render(<App />, document.getElementById("app"))
  </script>
</body>

</html>